Abstract Detail

Ecophysiology

Krogmeier, Katie [1], Neufeld, Howard [2], Pauer, Erica [1].

Investigating Potential Impacts of Polyploidy on the Ecophysiological Responses of Solidago altissima to Climate Change.

The evolutionary and ecological importance of polyploidy in plants is still a subject of much research. Polyploidy could be an evolutionary dead end or it could lead to reproductive isolation and creation of new species. How polyploidy impacts plant ecophysiology and responses to climate change are poorly understood and are the goals of this project. Goldenrod (Solidago altissima) is a North American herbaceous perennial with diploid, tetraploid, and hexaploid populations: diploids occur in the midwest and hexaploids in the midwest and east. We propose that the different geographic distributions of the polyploids result from natural selection for varying environmental conditions arising from differences in morphology and ecophysiology. For example, polyploids have larger cells, which can affect stomatal densities, sizes, and kinetics, and ultimately gas exchange rates. We conducted gas exchange measurements on potted plants outdoors at the Appalachian State University greenhouse using the Li-6800 in the summer of 2018. Measurements at saturating light were made in July and light response curves were made in September. Rates of photosynthesis were higher in July than September for all populations and highest for diploids compared to hexaploids, which did not differ (20.4 vs 16.6 µmol m⁻² s⁻¹, p = 0.042). There were no population differences in stomatal conductance, transpiration or water use efficiency. In September, maximum photosynthetic rates were still lowest for eastern hexaploids, but midwest hexaploid rates remained elevated and were not distinguishable from diploids (12.8 vs 9.6 µmol m⁻² s⁻¹, p = 0.031). The drop in photosynthetic rates in September may have resulted from leaf aging and/or rust infection, which became prominent late in the season, even though only uninfected leaves were measured for gas exchange. We are currently making SEM and light microscopy measurements on leaf cross sections to ascertain morphological differences in cell size and leaf structure between cytotypes. This summer, a drought experiment will be conducted to investigate any ecophysiological differences between all 3 populations under future projected drought conditions. Plants from each region will be grown together, indoors at the ASU Greenhouse with half watered regularly and half subjected to progressive drought in a split-plot design. Measurements will be taken before, during, and after 2 experimental cycles on gas exchange, stomatal kinetics, growth, and stress between each population. These results will be used in conjunction with the SEM and light microscopy measurements to determine how morphological differences may influence physiological responses among cytotypes.